Deoxyribonucleic acid-guided dual-mode electro-chemical/chemiluminescent platform for sensitive and selective examination of Pb2+

Lead ion (Pb 2+ ) exposure is a serious hazard to human health, and its detection is still faced with undesirable bottleneck problems (poor sensitivity/selectivity and insufficient accuracy). Herein, a new dual-mode analytical platform for Pb 2+ assay is developed by integrating electrochemical (EC) with electro-chemiluminescent (ECL) system. It all starts with the shearing action of Pb 2+ to Pb 2+ -special DNAzyme (Pb-DNAzyme), and the substrate strand is cleaved at its cleavage site to result in two pieces of DNA, which are employed separately to construct the expected dual-mode biosensor. Interestingly, for EC mode, the Pb 2+ act as not only the target but also the inducing factor of the formation of in-situ G4 nanostructure, and the SWV technique is taken to achieve the signal output of the stacked crystal violet molecules. Furtherly, the other released DNAs can be captured by the three handing sides of DNA nano-prism, and trigger subsequently the opening of DNA hybridization chain reaction; then the designed free three bases can bring about TdT polymeric reaction; finally, by taking advantage of DNA nanoprobe, the dual-mode biosensor is developed successfully with the detection limit of 3.6 pM (EC) or 0.23 pM (ECL) (3δ/slope), which is much lower than the previous reports. This co-operative dual-mode method is also investigated for the analysis of Pb 2+ in the serum and lake water samples with acceptable results, presenting great potential applications in the future.